管输原油流量计系数交接计量方法与误差

Custody Transfer Metering Method Based on Flowmeter Coefficient and Its Process Error During Pipeline Transportation of Crude Oil

目前国内管道输送企业与各炼化企业进行原油交接计量主要采用流量计系数区间法。为了克服流量计特性曲线漂移所产生的误差,需对两次检定系数采用算术平均值法进行修正。两次检定期间实际交油质量的总和与采用基本误差法结算油量的总和的差量,在每次流量计检定结束后的油量结算中多退少补。给出了油量计算公式和计量参数读取规则,结合实际算例,介绍了该方法在原油计量结算应用中的计算全过程,包括求取流量计在某排量下的系数MF值、原油体积压力修正系数Cpi、原油体积温度修正系数Cti、原油在20℃时对应的标准体积V20、含水原油质量m、纯油量ma、含水量ms、补差油量mB。分析了交接计量过程中误差的产生原因,包括原油物性和温度,管道运行压力、计量设备运行状况、人为操作等因素,提出了减小误差的对策,对原油交接计量工作具有普遍的指导意义。

At present,domestic pipeline transportation enterprises and refinery enterprises mainly use flowmeter coefficient interval method on crude oil custody transfer metering.In order to eliminate the drift error of flowmeter characteristic curve,correction is done by calculating the mean value of two calibration coefficients.The subtraction of the real custody transfer amount and the amount by basic error method during two calibrations follows the 'back much & little repair' rule at the end of each time oil settlement after flowmeter calibration.This paper provides the oil amount formula and read rule of metering parameters.Associa-ted with the practical example,the overall calculation procedure is introduced for crude oil metering settlement with this method,including the calculation of coefficient MF of a flowmeter under a specific displacement,crude oil volume pressure correction coefficient C■.crude oil volume temperature correction coefficient Ct■,crude oil standard volume under 20 ℃ V20,mass of water-cut crude oil m.pure oil mass ma,water amount m5 and make up difference oil m3.Also,the reasons of custody transfer error produced are analyzed,including the property and temperature of crude oil,pipeline operation pressure,running status of metering devices and personal factors.The error control solution is presented,which is of significance in crude oil custody transfer operation.